Corrugated Packaging 101
By Melissa Montague, Wexxar Packaging Inc.
The purpose of this paper is to help businesses (large and small) develop an appreciation
for the science of corrugated material and understand the purpose behind different box
designs. Both corrugated material and the boxes and trays that are formed from it are
constructed for the specific packaging and shipping needs of businesses in various
industries.
Once the science of corrugated material, the standards that govern the corrugated industry
and the purpose box and tray construction has been explained, it will dispel the myth,
“any old box will do.”
The Challenge
Each business in each industry faces its own unique challenges when it comes to
packaging and shipping its products, but they share the same goal: To get its products to
market safely.
Proper packaging, which includes choosing the proper corrugated material and box (or
tray) design, is an important factor in reducing the cost associated with losing products to
damage.
What is Corrugated?
Corrugated material is comprised of two main components: a liner and a
wavy, fluted material. The fluted material is inserted between two liners
and gives the material its strength, similar to the way arches provide
strength to a bridge. The liners and fluted material are then glued,
pressed, cut and scored on a corrugator.
Basic Box Construction
All corrugated boxes and trays start out as flat sheets of corrugated material. If a box
requires printing, it is transported to a press, which prints graphics directly on the flat
sheet. Once printed, the box is fed through a flexo-folder gluer, which applies cross slots
and cross scores to create the individual flaps, and applies cold glue on the
manufacturer’s joint (the end flap used to glue the box together), folds, and compresses
the box.
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Corrugated boxes are popular because of their strength and because they can be produced
in high volumes very quickly and easily.
Standards of Corrugated Material
There are four basic standards used in constructing corrugated material:
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Board styles
Flutes
Dimensions
Edge crush test
Board Styles
There are four standard thicknesses of corrugated material:
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Single face: In which one piece of fluted material is glued to one piece of liner.
Single wall: In which one piece of fluted material is glued between two pieces of
liner.
Double wall: In which two pieces of fluted material is glued between three pieces
of liner.
Triple wall: In which three pieces of fluted material is glued between four pieces
of liner.
Flutes
The wavy, fluted material, found between sheets of liner material, is commonly referred
to as “Flutes”. The flutes themselves give the material its strength, allowing it to sustain a
great deal of weight. It also provides a degree cushion to help protect the contents inside
the box.
Flutes come in various standard sizes (A, B, C, E, and F). A-flute was the first type of
corrugated to be developed, followed by B-flute, which is thinner. C-flute, the most
common thickness used, lies between A and B. Both E-flute and F-flute (also known as
fine flute) are respectively thinner than B-flute.
Dimensions
The dimensions of a corrugated box are always measured from the inside of the box and
are expressed as length x width x height. The length is always the first dimension to be
expressed and should always be the highest number of the three.
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Edge Crush Test
Edge Crush Test (ECT) is the standard by which box strength is measured. It specifies the
amount of force a piece of corrugated material can withstand before it fails. The ECT
measurement is expressed in pounds per square inch and can often be found on the round
printed label containing box specifications.
Strengthening Strategies
There are three main ways to add strength to a corrugated box.
1) Vertical fluting: boxes are constructed so the flutes always run vertically, giving it
its stacking strength.
2) Thickness and board styles: boxes can be constructed using double or triple wall
with a combination of different fluting, such as A-flute and C-flute between the
liners.
3) Lugs and flanges: boxes can incorporate additional material in their design such
as slotted lugs, re-enforced corner posts, and flanges inserted at each end to
provide additional stacking strength.
Corrugated Box Construction
Depending on which industry the business is operating in and what type of products they
produce will often command which type of box they will use.
Regular Slotted Cases
The most common box used in packaging is the Regular Slotted Case (RSC). This box
features two major flaps, which run the length of the box, and two minor flaps at each
end. The major flaps overlap the minor flaps when folded. The longer the box is, the less
overlap exists among the flaps. The more square the box is, the more overlap exists. The
overlap adds to the strength of the box, however the flaps of an RSC box can also be cut
away to save on material.
RSC Variations
The RSC is a standard box construction with many variations, which include:
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Half Slotted Case (HSC)
Centre Special-Slotted Container (CSSC)
An HSC is essentially an RSC with the top flaps removed. It is frequently used as a tray
or inner box and is incorporated with an outer box, which forms the lid. The HSC is used
commonly within the fruit industry since the lid can simply be removed to access the
product inside without cutting, which can cause damage. Industries where products can
be damaged by cutting quite often opt for the HSC type.
The CSSC derivative also referred to as an All Flaps Meet (AFM) box is an RSC in
which both major and minor flaps meet at the centre of the box when folded. This style of
box creates a flat floor, which prevents paper cuts or abrasions on products caused by
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paper edges. This type of box also features an extra strong top and bottom provided by
the full overlap.
RSC Applications
Small boxes used by industries such as the pharmaceutical industry feature bottom flaps
that meet and are taped. The top flaps also meet and are taped, however these flaps may
be cut back to save material. This style of flap is often referred to as “shy” or “econo”
flaps.
Tray Form Boxes
The difference between a box and a tray is that a tray features a one-piece bottom. Trays
are often used in the food and beverage industry to hold soft drink cans, pack meat, and
stack fruits and vegetables. Trays are also often produced as lids for HSC boxes.
There are two types of trays: Glued Tray and Self-locking Tray.
Glued Trays
Glued Trays feature small flaps that are glued during the forming process. From a
material perspective, Glued Trays are more economical than Self-locking Trays because
they tend to have a lot less material in them.
Self-locking Trays
Self-locking Trays feature tabs, which can be folded and locked into recesses cut out of
the tray. Self-locking Trays are a particularly useful tray because they can be formed by
hand in small volumes or they can be formed automatically by tray formers in larger
volumes.
Tray Applications
Trays are particularly useful in the food and beverage industry and are constructed in
many different styles, including:
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Slotted tray
Tray with top flaps
Bag in box
Display tray
One-piece telescoping tray
Multi-use box (MUB) tray
Bliss Boxes
Although it is technically a tray box, the Bliss box is unlike any other tray because it is
made from three pieces of material, whereas a tray box is made from one piece of
material. Like a tray, the body is made from a single piece of material, which forms the
bottom, sides, and major flaps at the top. However, each end is made of a separate piece
of material, featuring a minor flap. The bottom and sides feature overlapping flanges into
which the end panels are glued and attached to the main body. This design provides much
more strength than an RSC.
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The Bliss Box design allows customers to get a lot more strength from the box and save
money by using a lighter material for the body and a heavier material for the sides for
stacking strength. Additional stacking strength is provided by having flutes run vertically.
Bliss Box Variations
Some Bliss Box designs feature end panels with no minor flap, which can help save on
material if minor flaps are not needed. Another style of Bliss Box features a center
divider made from two pieces of material on which the flaps can overlap, providing a
bridge across the centre divider.
The body of a Bliss Box can sometimes contain perforations or a tear out which allows
customers to display the contents of the box without opening it. Similarly, another style
uses a Bliss inner box and an HSC outer box, containing major flaps. This allows the
customer to remove the outer box, leaving the Bliss inner box to hold the product. This
style of box is very popular within the fruit industry.
Bliss Box Applications
The Bliss box lends itself to many different uses. It is primary used in agriculture for
packing fruits, vegetables, and meat as well as in the construction industry to hold heavier
items. In fact, Bliss Boxes can be used in any industry that requires stacking strength.
Summary
No matter what industry a business finds itself in, if its goal is to get its product to market
safely, it must become aware of the different packaging materials and methods available
in order to avoid damage during shipping. Corrugated materials and box (or tray)
construction itself will not ensure the safe delivery of products but it is an important part
of the process.
Understanding what materials and designs are used in the construction of corrugated
boxes and which materials and designs best suit a businesses needs is the first step in
getting their products to market safely. It is also the first step in developing a strategy for
forming boxes, packing them, and shipping them.
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